(C) Decrypt a SAML Response

Demonstrates how to decrypt a SAML response.

Note: This example requires Chilkat v9.5.0.76 or greater.

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#include <C_CkHttp.h>
#include <C_CkStringBuilder.h>
#include <C_CkXml.h>
#include <C_CkPrivateKey.h>
#include <C_CkRsa.h>
#include <C_CkBinData.h>
#include <C_CkCrypt2.h>

void ChilkatSample(void)
    {
    HCkHttp http;
    HCkStringBuilder sbSamlResponse;
    HCkStringBuilder sbPrivateKeyPem;
    BOOL success;
    HCkXml xml;
    HCkPrivateKey privkey;
    HCkRsa rsa;
    const char *encryptedAesKey;
    HCkBinData bdAesKey;
    HCkStringBuilder sbRsaAlg;
    const char *encrypted64;
    HCkBinData bdEncrypted;
    HCkCrypt2 crypt;
    HCkStringBuilder sbAlg;
    const char *decryptedXml;
    HCkXml xmlAssertion;
    HCkXml xmlEncryptedAssertion;

    //  This example requires the Chilkat API to have been previously unlocked.
    //  See Global Unlock Sample for sample code.

    //  This example decrypts this SAML response:

    //  <?xml version="1.0" encoding="UTF-8" ?>
    //  <saml2p:Response Destination="https://deskflow-asp2.com/ubc/ubcdfe.dll/cwlacs" ID="_e4585eaeedbcaf7c24dff7f1ee2499f5" IssueInstant="2018-10-11T17:46:20.727Z" Version="2.0" xmlns:saml2p="urn:oasis:names:tc:SAML:2.0:protocol">
    //      <saml2:Issuer xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion">https://authentication.stg.id.ubc.ca</saml2:Issuer>
    //      <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
    //          <ds:SignedInfo>
    //              <ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
    //              <ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha256"/>
    //              <ds:Reference URI="#_e4585eaeedbcaf7c24dff7f1ee2499f5">
    //                  <ds:Transforms>
    //                      <ds:Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"/>
    //                      <ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
    //                  </ds:Transforms>
    //                  <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/>
    //                  <ds:DigestValue>1ui22tqFyYEOoWI19CMwz4n+ynxNjLDGdTeRMdi60EU=</ds:DigestValue>
    //              </ds:Reference>
    //          </ds:SignedInfo>
    //          <ds:SignatureValue>ROg7FXV6vsp8socVhdo76/i7cRHGGKIveAiScKdujZT0QrHVqIvvbZ/RnwvEMJ9H9i/kJFAQA171
    //  		Eo2kDjSdvNFQ/YcKaJUwMtAwT05yVatGV42RZKEf7ME+vpcCTR1LWZdrhat1FWCg1MNQwNWB0EL5
    //  		fEP2a4jAcSTB8tFbjTAHsv7IWC39E5RVv99mACYXLa7iGZLtORANZxgYu5qQgmH6pUkI6Z1cpmf+
    //  		m9mIjKM6LF0EvLfWOBWL6udZ+GsHPOLjVTJg+1S0xb9FQCYDVW1QhbjSS0icKHKTNNbrsaxllVDY
    //  		m4q27YQjRh+XxugPgvsZ61Pxlto8Jbg+6jUlMQ==</ds:SignatureValue>
    //          <ds:KeyInfo>
    //              <ds:X509Data>
    //                  <ds:X509Certificate>MIIDTTCCAjWgAwIBAgIVAJccYyIV6wly8XyddumpgnHMJ2JLMA0GCSqGSIb3DQEBCwUAMCcxJTAj
    //  			BgNVBAMMHGF1dGhlbnRpY2F0aW9uLnN0Zy5pZC51YmMuY2EwHhcNMTcwMzAxMTk1NDM0WhcNMzcw
    //  			...
    //  			xUuh6HuHKIwQqHBz7udxbH3Zbb6jXGDJjiDHt1LRJ8xbVisFIcDlIwsGQQi0HeEJfx4P</ds:X509Certificate>
    //              </ds:X509Data>
    //          </ds:KeyInfo>
    //      </ds:Signature>
    //      <saml2p:Status>
    //          <saml2p:StatusCode Value="urn:oasis:names:tc:SAML:2.0:status:Success"/>
    //      </saml2p:Status>
    //      <saml2:EncryptedAssertion xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion">
    //          <xenc:EncryptedData Id="_314d80b9cf02d8eda8d686a6ffd626cf" Type="http://www.w3.org/2001/04/xmlenc#Element" xmlns:xenc="http://www.w3.org/2001/04/xmlenc#">
    //              <xenc:EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#aes128-cbc" xmlns:xenc="http://www.w3.org/2001/04/xmlenc#"/>
    //              <ds:KeyInfo xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
    //                  <xenc:EncryptedKey Id="_d7b6da6fb59a627ebb4a96928441ab79" Recipient="https://ubcdfe.deskflow-asp2.com" xmlns:xenc="http://www.w3.org/2001/04/xmlenc#">
    //                      <xenc:EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p" xmlns:xenc="http://www.w3.org/2001/04/xmlenc#">
    //                          <ds:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" xmlns:ds="http://www.w3.org/2000/09/xmldsig#"/>
    //                      </xenc:EncryptionMethod>
    //                      <ds:KeyInfo>
    //                          <ds:X509Data>
    //                              <ds:X509Certificate>MIICuzCCAiQCCQD3bpigRnKMSzANBgkqhkiG9w0BAQsFADCBoTELMAkGA1UEBhMCQ0ExEDAOBgNV
    //  				BAgMB09udGFyaW8xEDAOBgNVBAcMB1Rvcm9udG8xJjAkBgNVBAoMHVRhY3RpY2FsIEJ1c2luZXNz
    //  				...
    //  				kVRcHd1UK3q7G8FoykWjdQz/0EoMTfEZ+Md56mLOe48eMUZV2ONZuL1kDCEKw1UwkaDQI4Pf8pzx
    //  				82b9rgw9wBDtvu5eFPlUGEGIBw==</ds:X509Certificate>
    //                          </ds:X509Data>
    //                      </ds:KeyInfo>
    //                      <xenc:CipherData xmlns:xenc="http://www.w3.org/2001/04/xmlenc#">
    //                          <xenc:CipherValue>BNHfUOpgdPE5BgpN2VIZIDthMAv1rxk91qVnWyCZOG9bmUKChJtTUqMpndot7VJwYuyKFshkAdnT
    //  				D79KGdlSA1xHKcVeZXXzDWglqSyYjzhDCsyOhPaI4HelMFgCLwyFz89uEpUpqlvfl8ol3Am/XnzQ
    //  				Vp7V7oS76hocjUI51Qs=</xenc:CipherValue>
    //                      </xenc:CipherData>
    //                  </xenc:EncryptedKey>
    //              </ds:KeyInfo>
    //              <xenc:CipherData xmlns:xenc="http://www.w3.org/2001/04/xmlenc#">
    //                  <xenc:CipherValue>R6l7tmbnXrOfBgB8lA3KnwLYsLH5ZO5omQ7Hp5K05atzw2o55xmCXVMYhNneFxMtxUh6raEyHeZX
    //  			PTZNgWrvdqc4GYND/R7MhRrJzk9OAq1WyoOXwbtRpwNDwWA4N2IuprPQJbvjVxaw/PesZMZwZqlp
    //  			...
    //  			zm9zAxahyu8Ooe8M4r3HN2cY0JxxxkZtDiulbnyA+rRtXfBRJtangvFQ4iFAnzM/Yg9hMyW9jcu0
    //  			S7FzuRB9ONMxi+nh0IFWgqp+</xenc:CipherValue>
    //              </xenc:CipherData>
    //          </xenc:EncryptedData>
    //      </saml2:EncryptedAssertion>
    //  </saml2p:Response>

    //  The sample encrypted SAML response and RSA private key are available online:
    http = CkHttp_Create();
    sbSamlResponse = CkStringBuilder_Create();
    sbPrivateKeyPem = CkStringBuilder_Create();
    success = CkHttp_QuickGetSb(http,"https://chilkatdownload.com/data/samlresponse.xml",sbSamlResponse);
    if (success == TRUE) {
        success = CkHttp_QuickGetSb(http,"https://chilkatdownload.com/data/samlresponse_privkey.pem",sbPrivateKeyPem);
    }

    if (success != TRUE) {
        printf("%s\n",CkHttp_lastErrorText(http));
        CkHttp_Dispose(http);
        CkStringBuilder_Dispose(sbSamlResponse);
        CkStringBuilder_Dispose(sbPrivateKeyPem);
        return;
    }

    xml = CkXml_Create();
    CkXml_LoadSb(xml,sbSamlResponse,TRUE);

    //  Load the RSA private key..
    privkey = CkPrivateKey_Create();
    success = CkPrivateKey_LoadPem(privkey,CkStringBuilder_getAsString(sbPrivateKeyPem));
    if (success != TRUE) {
        printf("%s\n",CkPrivateKey_lastErrorText(privkey));
        CkHttp_Dispose(http);
        CkStringBuilder_Dispose(sbSamlResponse);
        CkStringBuilder_Dispose(sbPrivateKeyPem);
        CkXml_Dispose(xml);
        CkPrivateKey_Dispose(privkey);
        return;
    }

    //  Prepare an RSA object w/ the private key...
    rsa = CkRsa_Create();
    success = CkRsa_ImportPrivateKeyObj(rsa,privkey);
    if (success != TRUE) {
        printf("%s\n",CkRsa_lastErrorText(rsa));
        CkHttp_Dispose(http);
        CkStringBuilder_Dispose(sbSamlResponse);
        CkStringBuilder_Dispose(sbPrivateKeyPem);
        CkXml_Dispose(xml);
        CkPrivateKey_Dispose(privkey);
        CkRsa_Dispose(rsa);
        return;
    }

    //  RSA will be used to decrypt the xenc:EncryptedKey
    //  The bytes to be decrypted are in xenc:CipherValue (in base64 format)
    encryptedAesKey = CkXml_getChildContent(xml,"saml2:EncryptedAssertion|xenc:EncryptedData|ds:KeyInfo|xenc:EncryptedKey|xenc:CipherData|xenc:CipherValue");
    if (CkXml_getLastMethodSuccess(xml) != TRUE) {
        printf("Encrypted AES key not found.\n");
        CkHttp_Dispose(http);
        CkStringBuilder_Dispose(sbSamlResponse);
        CkStringBuilder_Dispose(sbPrivateKeyPem);
        CkXml_Dispose(xml);
        CkPrivateKey_Dispose(privkey);
        CkRsa_Dispose(rsa);
        return;
    }

    printf("Encrypted AES key (base64) = %s\n",encryptedAesKey);

    bdAesKey = CkBinData_Create();
    CkBinData_AppendEncoded(bdAesKey,encryptedAesKey,"base64");

    sbRsaAlg = CkStringBuilder_Create();
    CkStringBuilder_Append(sbRsaAlg,CkXml_chilkatPath(xml,"saml2:EncryptedAssertion|xenc:EncryptedData|ds:KeyInfo|xenc:EncryptedKey|xenc:EncryptionMethod|(Algorithm)"));
    printf("sbRsaAlg contains: %s\n",CkStringBuilder_getAsString(sbRsaAlg));
    if (CkStringBuilder_Contains(sbRsaAlg,"rsa-oaep",TRUE) == TRUE) {
        CkRsa_putOaepPadding(rsa,TRUE);
    }

    //  Note: The DecryptBd method is introduced in Chilkat v9.5.0.76
    success = CkRsa_DecryptBd(rsa,bdAesKey,TRUE);
    if (success != TRUE) {
        printf("%s\n",CkRsa_lastErrorText(rsa));
        CkHttp_Dispose(http);
        CkStringBuilder_Dispose(sbSamlResponse);
        CkStringBuilder_Dispose(sbPrivateKeyPem);
        CkXml_Dispose(xml);
        CkPrivateKey_Dispose(privkey);
        CkRsa_Dispose(rsa);
        CkBinData_Dispose(bdAesKey);
        CkStringBuilder_Dispose(sbRsaAlg);
        return;
    }

    printf("Decrypted AES key (hex) = %s\n",CkBinData_getEncoded(bdAesKey,"hex"));

    //  Get the encrypted XML (in base64) to be decrypted w/ the AES key.
    encrypted64 = CkXml_getChildContent(xml,"saml2:EncryptedAssertion|xenc:EncryptedData|xenc:CipherData|xenc:CipherValue");
    if (CkXml_getLastMethodSuccess(xml) != TRUE) {
        printf("Encrypted data not found.\n");
        CkHttp_Dispose(http);
        CkStringBuilder_Dispose(sbSamlResponse);
        CkStringBuilder_Dispose(sbPrivateKeyPem);
        CkXml_Dispose(xml);
        CkPrivateKey_Dispose(privkey);
        CkRsa_Dispose(rsa);
        CkBinData_Dispose(bdAesKey);
        CkStringBuilder_Dispose(sbRsaAlg);
        return;
    }

    bdEncrypted = CkBinData_Create();
    CkBinData_AppendEncoded(bdEncrypted,encrypted64,"base64");

    //  Get the symmetric algorithm:  "http://www.w3.org/2001/04/xmlenc#aes128-cbc"
    //  and set the symmetric decrypt properties.
    crypt = CkCrypt2_Create();
    sbAlg = CkStringBuilder_Create();
    CkStringBuilder_Append(sbAlg,CkXml_chilkatPath(xml,"saml2:EncryptedAssertion|xenc:EncryptedData|xenc:EncryptionMethod|(Algorithm)"));
    if (CkStringBuilder_Contains(sbAlg,"aes128-cbc",TRUE) == TRUE) {
        CkCrypt2_putCryptAlgorithm(crypt,"aes");
        CkCrypt2_putKeyLength(crypt,128);
        CkCrypt2_putCipherMode(crypt,"cbc");
        //  The 1st 16 bytes of the encrypted data are the AES IV.
        CkCrypt2_SetEncodedIV(crypt,CkBinData_getEncodedChunk(bdEncrypted,0,16,"hex"),"hex");
        CkBinData_RemoveChunk(bdEncrypted,0,16);
    }

    //  Other algorithms, key lengths, etc, can be supported by checking for different Algorithm attribute values..

    CkCrypt2_SetEncodedKey(crypt,CkBinData_getEncoded(bdAesKey,"hex"),"hex");

    //  AES decrypt...
    success = CkCrypt2_DecryptBd(crypt,bdEncrypted);
    if (success != TRUE) {
        printf("%s\n",CkCrypt2_lastErrorText(crypt));
        CkHttp_Dispose(http);
        CkStringBuilder_Dispose(sbSamlResponse);
        CkStringBuilder_Dispose(sbPrivateKeyPem);
        CkXml_Dispose(xml);
        CkPrivateKey_Dispose(privkey);
        CkRsa_Dispose(rsa);
        CkBinData_Dispose(bdAesKey);
        CkStringBuilder_Dispose(sbRsaAlg);
        CkBinData_Dispose(bdEncrypted);
        CkCrypt2_Dispose(crypt);
        CkStringBuilder_Dispose(sbAlg);
        return;
    }

    //  Get the decrypted XML
    decryptedXml = CkBinData_getString(bdEncrypted,"utf-8");
    printf("Decrypted XML:\n");
    printf("%s\n",decryptedXml);

    //  The decrypted XML looks like this:

    //  <saml2:Assertion xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion" ID="_226e565c548db7986d165d7d969b48b4" IssueInstant="2018-10-11T17:46:20.727Z" Version="2.0">
    //  ...
    //  ...
    //  ...
    //  </saml2:Assertion>

    xmlAssertion = CkXml_Create();
    CkXml_LoadXml(xmlAssertion,decryptedXml);

    //  Replace the saml2:EncryptedAssertion XML subtree with the saml2:Assertion XML.
    xmlEncryptedAssertion = CkXml_FindChild(xml,"saml2:EncryptedAssertion");
    CkXml_SwapTree(xmlEncryptedAssertion,xmlAssertion);
    CkXml_Dispose(xmlEncryptedAssertion);

    //  The decrypted XML assertion has now replaced the encrypted XML assertion.
    //  Examine the fully decrypted XML document:
    printf("Full XML SAML document with decrypted assertion:\n");
    printf("%s\n",CkXml_getXml(xml));


    CkHttp_Dispose(http);
    CkStringBuilder_Dispose(sbSamlResponse);
    CkStringBuilder_Dispose(sbPrivateKeyPem);
    CkXml_Dispose(xml);
    CkPrivateKey_Dispose(privkey);
    CkRsa_Dispose(rsa);
    CkBinData_Dispose(bdAesKey);
    CkStringBuilder_Dispose(sbRsaAlg);
    CkBinData_Dispose(bdEncrypted);
    CkCrypt2_Dispose(crypt);
    CkStringBuilder_Dispose(sbAlg);
    CkXml_Dispose(xmlAssertion);

    }